LAUSR

Molecular conformation has a striking function in dominating the molecular orientation, crystallinity, charge mobility, film morphology, and photovoltaic performance for classic donor−π–acceptor (D−π–A) type copolymers. Herein, we systematically investigate this correlation by modulating the chemical structures of conjugated polymers composed of a new emerging electron-donating building block of 4,8-bis(4-chlorothiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene (BDT-T-Cl). A D−π–A type copolymer PE31 is synthesized as the reference donor polymer, where BDT-T-Cl, benzotriazole (BTA), and thiophene (T) units are used as the D, A, and π-bridge, respectively. PE31 realizes a moderate power conversion efficiency (PCE) of 7.62% when paired with a nonfullerene acceptor Y6. The methoxy substitutes in the BTA unit leads to a twisted backbone conformation of the final polymer PE32, which has negative effects on the charge transport and results in a slightly reduced PCE of 7.31%. The intra/interchain noncovalent interacti...